Items of computerized automotive service equipment generally incorporate sensors located at the vehicle to provide indications of a vehicle's diagnostic state. For instance, wheel aligners utilize vehicle wheel angle sensors. Sometimes the sensors are not necessarily located at the vehicle, but are incorporated into an extravehicular apparatus, such as load unbalance detectors in wheel balancers. Recent designs have implemented personal computers in automotive service equipment. The current methods for coupling these sensors to the personal computer that performs the diagnostic evaluations and/or displays are through the computer's standard ports. In a modem PC, these include the serial port, the parallel port and internal ISA or PCI expansion slots (via an add-in board). The serial communications and parallel printer ports are the most convenient since they are standard on all PC's. Unfortunately, an operating system such as WINDOWS 3.1 or WINDOWS 95 typically expects that a printer, mouse, or modem is connected to serial communications and parallel printer ports. Connection of sensors to these ports often leads to conflicts in port addresses and available interrupts. Connecting sensors to the serial communications port is convenient but can be slow. Connecting sensors to the parallel printer port allows faster data transmission than the serial communications port but an additional printer port must then be added if a printer is desired. This again can lead to conflicts in port addresses and available interrupts. In both cases, to use a serial communications port or parallel printer port, a person knowledgeable about computers would most likely be required to configure the computer to support the connection of a sensor system.
An add-in sensor interface board allows very fast access to sensor information. Unfortunately, adding this board to a PC still requires a person knowledgeable of the computer to configure addresses and interrupts so there are no conflicts. Additionally, the physical layout of expansion slots is subject to change over time as newer models and protocols are developed, leading to obsolescence of current interface board specifications. Typically operating systems have no built-in support for a custom add-in board. Thus complex software must be written allowing the operating system and the automotive service program to communicate with the add-in board. This complex software must be re-written with the introduction of new, updated operating systems.
Still another problem in current systems exists when a single PC is required to support multiple sensor systems such as a wheel aligner combined with an engine analyzer. A PC has a limit to the number of add-in interface boards that can be added. There is a finite number of I/O addresses and interrupts that are available and once all of them are used, no additional boards may be added. The same problem exists if serial communications ports or parallel printer ports are used. Once the supported ports are used, it is difficult to add more. Furthermore, repair or replacement of interface boards may require specialized computer training for the automotive service technicians.